The technique of Yi was one of the paths Shen Lian set for himself. It was also his first step to try on destiny.
Regardless of Daoism, Buddhism, demons, or the various school of thoughts, the last stage of cultivation was not the thirst for strength. It was pointless for the celestials to opt for pure strength. There were many stars in space that was stronger than a celestial. Anyone of the stars had the strength to destroy the earth. This was something unachievable by any celestials.
However, a celestial that was able to see through the subtle path of revolving would be able to find a way to destroy the stars. Even those stars which never dim had no chance against the real, powerful celestial.
Therefore, strength and power may not be the same.